I've been hunting 4 years and I'm 16 now. I know you might think I'm ignorant because I'm young and play call of duty but I do know a lot about guns. In the four years I've hunted I've killed three deer all with the same gun which is a .243. It's only taken one shot each deer and the most they ran was about 40 yards. A .243 is about the lowest you want to go, but if you don't want to ruin all of the meat then you don't want to go much higher. A 308 is the highest I would go for deer but still that's going to blow the arms of a deer but it will surely do the job. You can get a .243 at a good price. My dad has had the one I hunt with since he was 13 and it still is as good as the day he got it.